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  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
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  <body>
    <script>
      const user = {
        username: "jack",
        age: 20,
        size: 200,
      };

      Object.freeze(user);

      user.age = 30;
      console.log(user);

      console.log(Object.isFrozen(user));
    </script>
  </body>
</html>
